U.S. patent number 6,205,828 [Application Number 09/379,893] was granted by the patent office on 2001-03-27 for forging die, and method and apparatus for controlling the same.
This patent grant is currently assigned to Honda Giken Kogyo Kabushiki Kaisha. Invention is credited to Yoshihisa Doi, Yuichi Nagao, Takeshi Tatsumi.
United States Patent |
6,205,828 |
Nagao , et al. |
March 27, 2001 |
Forging die, and method and apparatus for controlling the same
Abstract
A hydraulic pressure control apparatus comprises a high pressure
accumulator for sucking pressure oil supplied to a relief chamber
of a relief valve to make changeover for the relief valve from a
valve-closed state to a valve-open state when a forming load is
applied to the pressure oil charged in a pressure chamber and the
hydraulic pressure of the pressure oil arrives at a relief preset
pressure, and a low pressure accumulator for sucking the pressure
oil charged in the pressure chamber via the relief valve which is
in the valve-open state.
Inventors: |
Nagao; Yuichi (Omiya,
JP), Tatsumi; Takeshi (Tochigi-ken, JP),
Doi; Yoshihisa (Utsunomiya, JP) |
Assignee: |
Honda Giken Kogyo Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
27529982 |
Appl.
No.: |
09/379,893 |
Filed: |
August 24, 1999 |
Foreign Application Priority Data
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Aug 24, 1998 [JP] |
|
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10-237614 |
Sep 2, 1998 [JP] |
|
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10-248463 |
Sep 2, 1998 [JP] |
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10-248468 |
Sep 7, 1998 [JP] |
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10-252854 |
Sep 11, 1998 [JP] |
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10-258668 |
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Current U.S.
Class: |
72/4; 72/19.9;
72/20.2; 72/21.5; 72/373; 72/453.13 |
Current CPC
Class: |
B21J
9/12 (20130101); B21J 9/20 (20130101); B21K
1/762 (20130101); B21K 1/765 (20130101) |
Current International
Class: |
B21K
1/76 (20060101); B21K 1/00 (20060101); B21J
9/20 (20060101); B21J 9/12 (20060101); B21J
9/00 (20060101); B21B 033/02 () |
Field of
Search: |
;72/19.8,19.9,20.1,20.2,21.4,21.5,453.13,4,373,374 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tolan; Ed
Claims
What is claimed is:
1. A control apparatus for a forging die for forging a forging
material by relatively displacing a first die member and a second
die member to apply a pressurizing force of a punch member to said
forging material charged in a cavity said punch member being
movably disposed with respect to one of said first die member and
said second die member under action of a pressure fluid, said
control apparatus comprising:
a buffering mechanism for absorbing a residual displacement amount
of said punch member before arrival of said punch member at a
bottom dead center position within said cavity after abutment
between said first die member and said second die member, and then
permitting further movement of said punch member to said bottom
dead center position in said cavity in accordance with an action of
said pressure fluid charged in a pressure chamber as a result of
said relative displacement of said first die member and said second
die member; and
a discharge mechanism comprising a relief valve having a relief
chamber chargeable with said pressure fluid, for forcibly
discharging said pressure fluid from said pressure chamber to the
outside through said relief valve when a pressure of said pressure
fluid in said pressure chamber arrives at a relief preset pressure
as a result of application of a forming load to said pressure fluid
charged in said pressure chamber.
2. The control apparatus for said forging die according to claim 1,
wherein said relief valve communicates with said pressure chamber
via a passage, said discharge mechanism further comprising a first
accumulator for sucking said pressure fluid supplied to said relief
chamber of said relief valve to change said relief valve from a
valve-closed state to a valve-open state, and a second accumulator
for sucking said pressure fluid charged in said pressure chamber
through said relief valve when said relief valve is in said
valve-open state.
3. The control apparatus for said forging die according to claim 1,
wherein said pressure fluid is composed of pressure oil.
4. The control apparatus for said forging die according to claim 2,
wherein said first accumulator is composed of a high pressure
accumulator, said second accumulator is composed of a low pressure
accumulator, and said low pressure accumulator is designed to have
a volume which is larger than that of said high pressure
accumulator.
5. The control apparatus for said forging die according to claim 2,
further comprising a pressure control valve for controlling said
pressure of said pressure fluid to be supplied to said relief
chamber of said relief valve.
6. A control apparatus for a forging die for forging a forging
material by relatively displacing a first die member and a second
die member to apply a pressurizing force of a punch member to said
forging material charged in a cavity, said punch member being
movably disposed with respect to one of said first die member and
said second die member under action of a pressure fluid, said
control apparatus comprising
a buffering mechanism for absorbing a residual placement amount of
said punch member before arrival of said punch member at a bottom
dead center position within said cavity after abutment between said
first die member and said second die member, and then permitting
further movement of said punch member to said bottom dead center
position in said cavity in accordance with an action of said
pressure fluid charged in a pressure chamber as a result said
relative displacement of said first die member and said second die
member;
a pressure-detecting mechanism for detecting a pressure of said
pressure fluid charged in said pressure chamber; and
a pressure fluid control mechanism comprising a relief valve having
a relief chamber chargeable with said pressure fluid for
discharging said pressure fluid from said pressure chamber to the
outside through said relief valve if it is judged that said forging
material is not charged in said cavity when said pressure of said
pressure fluid charged in said pressure chamber does not arrive at
an initial preset pressure at an initial stage of forging, on the
basis of a detection signal outputted from said pressure-detecting
mechanism.
7. The control apparatus for said forging die according to claim 6,
wherein said relief valve includes an inlet port communicating with
said pressure chamber, said pressure fluid control mechanism
further comprising a solenoid-operated valve connected to a relief
port of said relief valve, for releasing a relief pressure of said
pressure fluid in said relief valve in accordance with a changeover
action.
8. The control apparatus for said forging die according to claim 6,
wherein said pressure fluid is composed of pressure oil.
9. The control apparatus for said forging die according to claim 6,
wherein said pressure-detecting mechanism is composed of a pressure
sensor, and a load sensor for detecting whether or not said first
die member abuts against said second die member is provided
separately from said pressure sensor.
10. The control apparatus for said forging die according to claim
6, further comprising an air vent circuit for removing air
contaminating said pressure fluid in said pressure chamber, wherein
said air contaminating said pressure fluid is discharged to the
outside together with said pressure fluid leaked from said pressure
chamber.
11. The control apparatus for said forging die according to claim
7, further comprising a pressure control valve for controlling said
pressure of said pressure fluid to be supplied to a relief chamber
of said relief valve.
12. A method for controlling a forging die for forging a forging
material by relatively displacing a first member and a second die
member to apply a pressurizing force of a punch member to said
forging material charged in a cavity, said punch member being
movably disposed with respect to one of said first die member and
said second die member under action of a pressure fluid charged in
a pressure chamber, said method comprising the steps of:
supplying said pressure fluid to said pressure chamber to a relief
chamber of a relief valve; allowing said first die member and said
second die member to make abutment before arrival of said punch
member at a bottom dead center position within said cavity as a
result of relative displacement of said first die member and said
second member;
allowing further movement of said punch member to said bottom dead
center position in said cavity;
absorbing a residual displacement amount of said punch member
before arrival of said punch member at said bottom dead center
position within said cavity after said abutment between said first
die member and said second die member; and
forcibly discharging said pressure fluid from said pressure chamber
to the outside through said relief valve when a forming load is
applied to said pressure fluid charged in said pressure chamber and
a pressure of said pressure fluid arrives at a relief preset
pressure.
13. The method for controlling said forging die according to claim
12, wherein said pressure fluid charged in said pressure chamber is
sucked into a second accumulator in accordance with a driving
action of said second accumulator after said pressure fluid
supplied to a said relief chamber of a said relief valve is sucked
in accordance with a driving action of a first accumulator to allow
said relief valve to be in a valve-open state.
14. The method for controlling said forging die according to claim
12, wherein said pressure fluid is composed of pressure oil.
15. The method for controlling said forging die according to claim
13, wherein said first accumulator is composed of a high pressure
accumulator, said second accumulator is composed of a low pressure
accumulator, and said low pressure accumulator has a volume which
is larger than that of said high pressure accumulator.
16. A method for controlling a forging die provided with buffering
mechanism for absorbing a residual displacement amount before
arrival of a punch member at a bottom dead center position within a
forging cavity after abutment between a first die member and a
second die member, said punch member being movably disposed with
respect to one of said first die member and said second die member
under action of a pressure fluid said method comprising the steps
of:
supplying said pressure fluid to a pressure chamber of said
buffering mechanism and to a relief chamber of a relief valve;
detecting whether or not a pressure of a pressure fluid charged in
said pressure chamber of said buffering mechanism arrives at an
initial preset pressure at an initial forging stage before said
first die member and said second die member make said abutment as a
result of relative placement of said first die member and said
second member, wherein if said pressure of said pressure fluid does
not arrive at said initial preset pressure, then it is judged that
no forging material is charged, in said cavity; and
forcibly discharging said pressure fluid charged in said pressure
chamber to the outside through said relief valve if said pressure
of said pressure fluid does not arrive at said initial present
pressure.
17. The method for controlling said forging die according to claim
16, wherein said pressure fluid charged said pressure chamber is
discharged to the outside by energizing a solenoid-operated valve
to release a relief pressure of said pressure fluid in said relief
valve.
18. The method for controlling said forging die according to claim
16, wherein said pressure fluid is composed of pressure oil.
19. The method for controlling said forging die according to claim
16, further comprising the steps of detecting said pressure of said
pressure fluid charged in said pressure chamber, and stopping said
relative displacement of said first die member and said second die
member if said pressure of said pressure fluid is without a
predetermined charge pressure range.
20. The method for controlling said forging die according to claim
16, further comprising the steps of detecting an abutment load upon
said abutment as a result of said relative displacement of said
first die member and said second die member, and stopping said
relative displacement of said first die member and said second die
member if said first die member and said second die member make no
abutment.
21. The method for controlling said forging die according to claim
16, further comprising the steps of detecting a relief pressure of
said pressure fluid in said pressure chamber until said arrival at
said bottom dead center after said abutment between said first die
member and said second die member, and stopping said relative
displacement of said first die member and said second die member if
said relief pressure is without a predetermined range.
22. The method for controlling said forging die according to claim
16, wherein air contaminating said pressure fluid in said pressure
chamber is removed to the outside together with said pressure fluid
leaked from said pressure chamber.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a forging die, and a method and an
apparatus for controlling the same, in which a forging material is
arranged in a cavity so that it may be forged in accordance with a
pressurizing action of a punch.
2. Description of the Related Art
A forging die has been hitherto known, which is used to forge a
forging material into a predetermined shape such that the forging
material is inserted into a cavity which is formed by an upper die
and a lower die joined to one another, and a pressurizing force is
applied to the forging material by the aid of a punch.
The present applicant has suggested a forging die which is provided
with a buffering mechanism for absorbing a residual displacement
amount corresponding to a range from abutment of a punch against a
lower die to arrival at a bottom dead center (Japanese Laid-open
Patent Publication No. 11-169996).
The buffering mechanism includes a piston which is provided
displaceably along a pressure chamber charged with a pressure oil.
The buffering mechanism functions to preferably absorb the residual
displacement amount of the punch by using the pressure oil charged
in the pressure chamber in accordance with a displacement action of
the piston.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide a method
and an apparatus for controlling a forging die, in which a high
pressure is applied without generating any surge pressure, and a
buffering function is preferably effected to absorb the forming
load by using a pressure fluid having a high discharge speed.
A principal object of the present invention is to provide a method
and an apparatus for controlling a forging die, in which if no
forging material is charged in a cavity, the die is prevented from
any damage even when an upper die and a lower die make abutment so
that the durability of the die is improved.
Another object of the present invention is to provide a forging
die, in which any strain of the die due to any stress is reduced to
improve the durability of the die, and the cost of the die is
lowered.
Still another object of the present invention is to provide a
forging die, in which the die is allowed to have a simplified
structure to improve the dividability, and the number of parts to
be exchanged due to secular change is made as small as possible so
that the cost may be reduced.
Still another object of the present invention is to provide a
forging die, in which any stress concentration, which would be
otherwise caused by tensioning, is suppressed to improve the
durability of the die, and thus the cost of the die can be
lowered.
The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings in which a preferred embodiment of the present invention
is shown by way of illustrative example.
DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal sectional view illustrating a forging
die incorporated with a hydraulic pressure control apparatus
according to a first embodiment of the present invention;
FIG. 2 illustrates the operation depicting a state in which the
forging process is completed after a punch is lowered from a
forging start position shown in FIG. 1;
FIG. 3 shows a circuit system including the hydraulic pressure
control apparatus;
FIG. 4 shows a longitudinal sectional view with partial omission
illustrating a state in which a forging material is charged in a
cavity;
FIG. 5 illustrates a production step of an outer cup for
constructing a constant velocity universal joint;
FIG. 6 illustrates a production step of the outer cup for
constructing the constant velocity universal joint;
FIG. 7 illustrates a production step of the outer cup for
constructing.the constant velocity universal joint;
FIG. 8 illustrates a production step of the outer cup for
constructing the constant velocity universal joint;
FIG. 9 illustrates the relationship between the displacement amount
of the punch and the pressure value of the pressure oil;
FIG. 10 illustrates the dimension of the bottom thickness of the
cup of the outer cup obtained as a forged product;
FIG. 11 shows a flow chart illustrating the operation of the
hydraulic pressure control apparatus according to the first
embodiment;
FIG. 12 illustrates the relationship between the time and the
hydraulic pressure of the pressure oil charged in a pressure
chamber;
FIG. 13 illustrates the output of a load sensor corresponding to
the change in hydraulic pressure in the pressure chamber concerning
a case in which a first plate and a second plate make abutment and
a case in which the first plate and the second plate make no
abutment;
FIG. 14 shows a longitudinal sectional view illustrating a forging
die according to a second embodiment of the present invention;
FIG. 15 illustrates the operation depicting a state in which the
forging process is completed after a punch is lowered from a
forging start position shown in FIG. 14;
FIG. 16 shows a partial magnified longitudinal sectional view
illustrating the forging die shown in FIG. 14;
FIG. 17 shows a plan view with partial cross section illustrating
the forging die shown in FIG. 14;
FIG. 18 shows a longitudinal sectional view taken along the axial
direction illustrating a guide means provided for the forging die
shown in FIG. 14;
FIG. 19 shows a cross-sectional view taken along a line XIX--XIX
shown in FIG. 18;
FIG. 20 shows a perspective view illustrating a guide sleeve to be
externally fitted to the punch;
FIG. 21 shows a longitudinal sectional view taken along the axial
direction illustrating a forged product forged by using the forging
die shown in FIG. 14;
FIG. 22 shows a longitudinal sectional view illustrating a forging
die according to a third embodiment of the present invention;
FIG. 23 illustrates the operation depicting a state in which the
forging process is completed after a punch is lowered from a
forging start position shown in FIG. 22;
FIG. 24 shows a partial magnified longitudinal sectional view
illustrating the forging die shown in FIG. 22;
FIG. 25 shows a magnified longitudinal sectional view illustrating
a part of G shown in FIG. 24;
FIG. 26 shows a magnified longitudinal sectional view illustrating
a part of H shown in FIG. 24;
FIG. 27 shows a longitudinal sectional view illustrating a forging
die according to a fourth embodiment of the present invention;
FIG. 28 shows a partial magnified longitudinal sectional view
illustrating the forging die shown in FIG. 27;
FIG. 29 shows a magnified longitudinal sectional view illustrating
a part of I shown in FIG. 28;
FIG. 30 illustrates a production step of an outer cup for
constructing a constant velocity universal joint;
FIG. 31 illustrates a production step of the outer cup for
constructing the constant velocity universal joint;
FIG. 32 shows a front view illustrating a forging material to be
charged in a cavity of the forging die shown in FIG. 27;
FIG. 33 shows a partial longitudinal sectional view illustrating a
forged product forged by using the forging die shown in FIG.
27;
FIG. 34 shows a magnified sectional view with partial omission for
illustrating the stress generated when the forged product is taken
out by using a lower die according to the fourth embodiment of the
present invention; and
FIG. 35 shows a magnified sectional view with partial omission for
illustrating the stress generated when a forged product is taken
out by using a lower die concerning Comparative Example.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIG. 1, reference numeral 11 indicates a forging
die which is incorporated with a hydraulic pressure control
apparatus 10 according to a first embodiment of the present
invention.
The forging die 11 comprises a first die holder 14 which is
provided with a plurality of guide means 12a 12d standing thereon
in the vicinity of four corners, and a second die holder 16 and a
third die holder 18 which are provided in a stacked manner at a
central portion of the first die holder 14.
A thick-walled forcible insertion ring 20, which is formed in an
integrated manner, is fixed on the second die holder 16 by the aid
of a clamping means 22. An upper die 26 and a lower die 28 are
joined in an integrated manner in a hole of the forcible insertion
ring 20 by the aid of a sleeve 24 which is formed to be
thin-walled.
A first ring member 34 formed with a hole 32, a second ring member
36 externally fitted to the first ring member 34, and a clamping
ring 38 for holding the first ring member 34 and the second ring
member 36 are provided in an annular recess 30 which is formed on
an upper side of the forcible insertion ring 20. The first ring
member 34 and the second ring member 36 are forcibly inserted with
good concentricity into a hole 37 which is formed on the upper side
of the forcible insertion ring 20 and which is machined
concentrically with a cavity 46 as described later on. In this
embodiment, the first ring member 34 and the second ring member 36
may be integrally formed as a ring member without constructing them
separately with each other.
A first plate 44, which regulates the displacement amount of a
punch 40 by making abutment against a second plate 42 that is
displaceable integrally with the punch 40 as described later on, is
provided on the upper surfaces of the upper die 26 and the sleeve
24. The upper die 26, the lower die 28, and other components
including the first plate 44 function as a first die member.
As shown in FIG. 4, the first plate 44 is provided with a load
sensor 45 for detecting whether or not the forming load is reliably
applied by the punch 40 to a forging material. In this embodiment,
the load sensor 45 is used to detect the fact that the second plate
42, which is displaced integrally with the punch 40, abuts against
the first plate 44. A detection signal, which is outputted from the
load sensor 45, is introduced into an unillustrated controller.
Thus, the controller judges whether or not the first plate 44 and
the second plate 42 make abutment to regulate the displacement
amount of the punch 40 so that the forging material is forged to
have a predetermined thickness dimension.
The first ring member 34 is formed of, for example, a metal
material such as cemented carbide. The first ring member 34 is in a
state of being strongly tightened toward the center by the second
ring member 36 which is subjected to the shrinkage fitting
treatment. The first ring member 34 and the second ring member 36
are forcibly inserted into the hole 37 which is machined
concentrically with the cavity 46, and they are constricted by a
tapered section of the clamping ring 38 which is screwed into the
screw hole of the forcible insertion ring 20. Thus, the first ring
member 34 and the second ring member 36 are joined in an integrated
manner to the recess 30 of the forcible insertion ring 20 with good
concentricity.
In this embodiment, the cavity 46 is formed by the upper die 26 and
the lower die 28. A knockout pin 48 for extruding the forged
product is arranged movably back and forth along a hole 50 which is
formed through the second die holder 16 and the third die holder
18. A secondary formed product 52 as shown in FIG. 8 is charged as
the forging material in the cavity 46.
An elevator unit 54, which is connected to a ram of an
unillustrated mechanical press and which is displaceable in the
vertical direction integrally with the ram in accordance with the
driving action of the mechanical press, is provided over the
forcible insertion ring 20 at a position separated by a
predetermined distance.
The elevator unit 54 includes a buffering mechanism 56 for
absorbing the residual displacement amount until arrival at the
bottom dead center after completion of the forging process for the
forging material in accordance with the abutment between the upper
die and the lower die before arrival at the bottom dead center
after the start of the forging process upon the abutment of the
punch 40 against the forging material.
The buffering mechanism 56 is formed with a pressure chamber 58 at
the inside thereof. The buffering mechanism 56 includes a bottomed
cylindrical block member 62 having a piston 60 which is provided
vertically displaceably along the pressure chamber 58, and a pair
of joint blocks 66a, 66b connected to the block member 62 in a
liquid-tight manner and formed with a passage 64 which communicates
with the pressure chamber 58. A ring-shaped stopper 68 for
preventing the piston 60 from downward movement is fixed on the
bottom surface of the block member 62.
A ring-shaped high pressure packing 72, a low pressure packing 74,
and a wear plate 76 are installed to the outer circumference of the
piston 60 by the aid of annular grooves. A punch plate 78 is fixed
to the bottom surface of the piston 60. The punch 40 is fixed to
the punch plate 78 by the aid of a holder which surrounds a part of
the outer circumferential surface. A guide sleeve 82, which is made
of a cylindrical metal material, is externally fitted to the outer
circumference of the holder 80. The second plate 42 is secured to
the bottom surface of the holder 80.
It is preferable that the guide sleeve 82 is made of, for example,
a metal material such as SKD 11, FC 25, or FC 30 based on JIS
(Japan Industrial Standard), and the first ring member 34 is made
of a material which is harder than that for the guide sleeve
82.
The holder 80 including the punch 40, the guide sleeve 82, the
second plate 42, and other components function as a second die
member. The punch 40 is provided displaceably in the vertical
direction integrally with the elevator unit 54 in accordance with
the guiding action of the plurality of guide means 12a to 12d
provided in the upstanding manner on the first die holder 14.
As shown in FIG. 1, the hydraulic pressure control apparatus 10
according to the first embodiment is fixed via a seal member 100 to
one of the joint blocks 66b. A hydraulic pressure source 102 is
connected to the hydraulic pressure control apparatus 10 via a tube
passage such as a tube.
As shown in FIG. 3, the hydraulic pressure control apparatus 10
includes a relief valve 104. The relief valve 104 has an inlet port
106 which communicates via the passage 64 with the pressure chamber
58 in which the piston 60 is accommodated, an outlet port 112 which
communicates via a discharge passage 108 with a tank 110 of the
hydraulic pressure source 102, and a relief port 116 which supplies
the relief pressure to an unillustrated relief chamber via a relief
pressure supply passage 114.
A supply passage 118, which is used to supply, to the pressure
chamber 58, the pressure oil stored in the tank 110 of the oil
pressure source 102 via a check valve 117 for the pilot operation,
is connected to an intermediate position of the passage 64. A
pressure sensor (pressure-detecting mechanism) 121, which is used
to detect the hydraulic pressure of the pressure oil in the
pressure chamber 58, is connected via a passage 119. The following
arrangement is available in place of the pressure sensor 121. That
is, a pair of unillustrated pressure sensors are used. Detection
signals, which are outputted from the pair of pressure sensors
respectively, are introduced into the unillustrated controller to
execute the detection by obtaining AND on the basis of the pair of
detection signals.
The relief valve 104 is constructed as follows. That is, when the
hydraulic pressure of the pressure oil charged in the pressure
chamber 58 exceeds the hydraulic pressure of the pressure oil
charged in the relief chamber, and an unillustrated valve plug is
displaced, then the valve-open state is given, in which the inlet
port 106 communicates with the outlet port 112. On the other hand,
when the hydraulic pressure of the pressure oil charged in the
pressure chamber 58 is not more than the hydraulic pressure of the
pressure oil charged in the relief chamber, the valve-closed state
is given, in which the communication between the inlet port 106 and
the outlet port 112 is blocked.
A high pressure accumulator (first accumulator) 124 is connected
via a check valve 122 for the pilot operation is connected to a
passage 120 which is branched from the relief pressure supply
passage 114. A low pressure accumulator (second accumulator) 128 is
connected to a passage 126 which is branched from the discharge
passage 108. The low pressure accumulator 128 is connected to the
supply passage 118 via a check valve 123 for the pilot operation.
It is preferable to use a piston type having a large volume for the
low pressure accumulator 128, and it is preferable to use a balloon
type for the high pressure accumulator 124.
The check valve 122 is normally in the valve-open state, and it is
in the valve-closed state in accordance with the action of pilot
pressure supply to keep the internal pressure of the high pressure
accumulator 124. Thus, the check valve 122 functions to protect the
high pressure accumulator 124.
The pressure chamber 58 is connected via a passage 125 to the input
side of an air vent circuit 127 for removing the air which
contaminates the pressure oil charged in the pressure chamber 58.
The output side of the air vent circuit 127 is connected via a
passage 129 to the discharge passage 108.
The air vent circuit 127 includes an air vent valve 131 composed of
a normally open type solenoid-operated valve. The air vent circuit
127 functions such that when the air vent valve 131 is in the
valve-open state, the air contaminating the pressure oil is
discharged via the discharge passage 108 to the tank 110 together
with a small amount of pressure oil leaked from the pressure
chamber 58. As a result, the air in the pressure oil charged in the
pressure chamber 58 is removed.
The relief pressure supply passage 114 is provided with a relief
pressure vent circuit 135 for making the relief preset pressure for
the relief valve 104 to be zero by discharging the pressure oil
stored in the relief chamber of the relief valve 104 to the
discharge passage 108 in accordance with the changeover action of a
relief pressure vent valve 133 composed of a solenoid-operated
valve. A passage 137, which communicates with the relief pressure
supply passage 114, is connected to the input side of the relief
pressure vent valve 133. On the other hand, a passage 139, which
communicates with the discharge passage 108, is connected to the
output side of the relief pressure vent valve 133. Reference
numeral 141 indicates a check valve.
In this embodiment, the relief valve 104, the relief pressure vent
valve 133, and the unillustrated controller function as a pressure
fluid control mechanism.
The hydraulic pressure source 102 includes the tank 110 in which
the pressure oil is stored, a first hydraulic pump 132 for feeding
the pressure oil via the supply passage 118 in accordance with the
driving action of a motor 130, and a second hydraulic pump 134 for
feeding the pressure oil to the relief chamber of the relief valve
104 via the relief pressure supply passage 114 in accordance with
the driving action of the motor 130.
A pressure control valve 136, which controls the relief pressure of
the relief valve 104 on the basis of a relief pressure control
signal introduced from the unillustrated controller, is interposed
between the second hydraulic pump 134 and the relief valve 104.
The forging die 11 incorporated with the hydraulic pressure control
apparatus 10 according to the first embodiment of the present
invention is basically constructed as described above. Next,
explanation will be made for the forming steps for the forging
material based on the use of the forging die 11. Explanation will
be made below for an illustrative case in which an outer cup for
constructing a constant velocity universal joint is forged and
formed to obtain a forged product.
The primary forging process is applied to a columnar billet 84 as
shown in FIG. 5 by using an unillustrated die apparatus to thereby
obtain a primary forged product 86 having different diameters of
those divided respectively by an intermediate step section as shown
in FIG. 6. Subsequently, the preliminary forming process is applied
to the primary forged product 86 (see FIG. 7), and then the
secondary forging process is performed by using another
unillustrated die apparatus. Thus, the secondary formed product 52,
which is composed of a cup section 88 and a shaft section 90 as
shown in FIG. 8, is obtained. The forging die 11 is used for the
secondary formed product 52 as a forging material to which the
tertiary forging process is further applied.
At first, the following preparatory operation is performed. That
is, the upper die 26, the lower die 28, the sleeve 24, the forcible
insertion ring 20, and the other components are assembled in an
integrated manner in a state in which the guide sleeve 82 is
inserted into the hole 32 of the first ring member 34. Thus, the
punch 40 is positioned with respect to the cavity 46 which is
formed by the upper die 26 and the lower die 28.
The pressure oil having a predetermined hydraulic pressure is
previously charged in the pressure chamber 58 via the supply
passage 118 and the passage 64 in accordance with the driving
action of the first hydraulic pump 132. The pressure oil is
supplied to the unillustrated relief chamber of the relief valve
104 via the relief pressure supply passage 114 in accordance with
the driving action of the second hydraulic pump 134 so that a
predetermined relief pressure is set. The relief preset pressure is
controlled by the pressure control valve 136 on the basis of the
relief pressure control signal introduced from the unillustrated
controller.
If an unillustrated protective circuit (overload mechanism) is
operated when any overload is generated, then a considerable period
of time is required to restore the ordinary operation state, and it
is impossible to continuously perform the forging process.
Therefore, the hydraulic pressure support load of the piston 60 is
set to be not less than the forming load on the forging material
and not more than the overload operation load. In this arrangement,
the forming load on the forging material is supported by the
pressure oil charged in the pressure chamber 58.
Subsequently, the secondary formed product 52 as the forging
material is charged into the cavity 46 in a state in which the
punch 40 is arranged at an unillustrated raised position (initial
position). The punch 40 is lowered integrally with the elevator
unit 54 which is joined to the ram in accordance with the driving
action of the unillustrated mechanical press to give the state
shown in FIG. 1. Thus, the forging process is started.
When the punch 40 is lowered integrally with the elevator unit 54,
any unbalanced load in the transverse direction is preferably
absorbed by the plurality of guide means 12a to 12d which are
provided between the elevator unit 54 and the first die holder 14.
Accordingly, the punch 40 can be smoothly inserted under the
pressure into the center of the hole 32 of the first and second
ring members 34, 36 arranged coaxially with the cavity 46 by the
aid of the guide sleeve 82.
When the forging process is started, the guide sleeve 82, which is
externally fitted to the part of the outer circumferential surface
of the punch 40, advances in accordance with the guiding action of
an unillustrated annular groove formed at the upper end of the hole
32 of the first ring member 34, and the punch 40 is further
lowered. Accordingly, the punch 40, the holder 80, and the guide
sleeve 82 are displaced in an integrated manner in a state of being
forcibly inserted into the hole 32 of the first ring member 34.
FIG. 9 shows the relationship between the displacement amount of
the punch 40 and the pressure oil charged in the pressure chamber
58. In FIG. 9, a curved line A depicted by a solid line indicates
the displacement amount of the punch 40 which is displaced
integrally with the ram in accordance with the driving action of
the unillustrated mechanical press. A curved line B depicted by a
two-dot chain line indicates the pressure value (hydraulic
pressure) of the pressure oil charged in the pressure chamber 58. A
curved line C depicted by a dashed line indicates the spacing
distance D (see FIG. 1) between the second plate 42 disposed on the
displacement side and the first plate 44 disposed on the fixed
side.
The ram of the unillustrated mechanical press is displaced
downwardly from the predetermined raised position, and the punch
40, the second plate 42, and the other components are lowered
integrally with the ram. Accordingly, the spacing distance D
between the first plate 44 on the fixed side and the second plate
42 on the displacement side is gradually decreased. The piston 60
is prevented from displacement in the downward direction by being
held by the stopper 68. The hydraulic pressure of the pressure oil
charged in the pressure chamber 58 is gradually increased in
accordance with the increase in load applied to the punch 40 after
the start of the forging process.
The second plate 42 abuts against the first plate 44 immediately
before the arrival at the bottom dead center as a result of the
further downward movement of the punch 40 from the state shown in
FIG. 1. That is, the spacing distance D between the first plate 44
and the second plate 42 is zero. Accordingly, the downward
displacement of the punch 40 is regulated, and the thickness for
the forging material is correctly regulated. Thus, the forging
process is completed.
The punch 40 is further lowered by a minute distance, and the
hydraulic pressure in the pressure chamber 58 arrives at the relief
preset pressure. Accordingly, the relief valve 104 is in the
valve-open state. The pressure oil in the pressure chamber 58 is
discharged to the outside to arrive at the state shown in FIG. 2 in
accordance with the stroking action of the piston 60.
When the pressure oil in the pressure chamber 58 is relieved, if
the outflow resistance of the pressure oil is high, then it is
feared that the so-called surge pressure is generated (see a broken
line in FIG. 9), in which the hydraulic pressure is instantaneously
increased to be not less than the relief preset pressure. In order
to avoid the occurrence of the surge pressure, it is necessary that
the valve plug of the relief valve 104 is quickly opened
immediately after the hydraulic pressure in the pressure chamber 58
arrives at the relief preset pressure so that the outflowing
pressure oil is rapidly discharged to the outside.
For this purpose, in the first embodiment, the pressure oil, which
is supplied to the relief chamber of the relief valve 104, is
sucked into the high pressure accumulator 124 in accordance with
the driving action of the high pressure accumulator immediately
after the hydraulic pressure in the pressure chamber 58 arrives at
the relief preset pressure. Therefore, the relief preset pressure
is suddenly decreased, and hence the valve plug is instantaneously
switched from the valve-closed state to the valve-open state.
Further, the relief valve 104 is in the valve-open state, and the
inlet port 106 communicates with the outlet port 112. Accordingly,
the passage 64 communicates with the discharge passage 108. The
large volume of the pressure oil, which is charged in the pressure
chamber 58, is discharged at a high discharge speed toward the tank
110 of the hydraulic pressure source 102 via the passage 64 and the
discharge passage 108 which make communication with each other.
During this process, the large volume of the pressure oil, which is
charged in the pressure chamber 58, is sucked into the low pressure
accumulator 128 in accordance with the driving action of the low
pressure accumulator 128. Therefore, it is possible to reduce the
flow passage resistance when the large volume of the pressure oil
charged in the pressure chamber 58 outflows along the discharge
passage 108, and it is possible to avoid the occurrence of the
surge pressure.
Although the pressure oil, which has passed through the relief
valve 104, is discharged at a high speed, it is substantially at
the ordinary pressure. Therefore, it is enough not to use the high
pressure accumulator but to use the low pressure accumulator having
the large volume. The pressure oil, which is temporarily stored in
the high pressure accumulator 124, passes through the check valve
122 and the relief pressure supply passage 114, and it is supplied
to the unillustrated relief chamber of the relief valve 104. On the
other hand, the pressure oil, which is temporarily stored in the
low pressure accumulator 128, passes through the check valve 123
and the supply passage 118, and it is supplied to the pressure
chamber 58.
As described above, in the first embodiment, the valve-closed state
and the valve-open state of the relief valve 104 are
instantaneously switched in accordance with the driving action of
the high pressure accumulator 124. The large volume of the pressure
oil, which is charged in the pressure chamber 58, is temporarily
stored in accordance with the driving action of the low pressure
accumulator 128. Thus, the pressure oil, which is applied with the
high pressure and which has the high discharge speed, is discharged
into the tank 110 without generating the surge pressure. As a
result, the forming load, which is applied to the forging material
during the forging process, is preferably supported by the pressure
oil charged in the pressure chamber 58. Thus, it is possible to
smoothly effect the buffering function.
In the first embodiment, the variation amount, which is caused by
the elongation of, for example, the frame of the unillustrated
mechanical press and the connecting rod and which would otherwise
cause the fluctuation of the thickness dimension of the forging
material in ordinary cases, is absorbed as the change in stroke
amount of the piston 60. Further, the thickness dimension of the
material is determined by the abutment of the upper and lower dies.
Therefore, no influence is exerted thereon by the elongation of,
for example, the frame and the connecting rod.
As described above, the dimension of the bottom thickness T (see
FIG. 10) of the cup section 94 of the outer cup obtained as the
forged product 92 is determined by the abutment between the second
plate 42 which is disposed on the side of the punch 40 and the
first plate 44 which is disposed on the side of the forcible
insertion ring 20. Therefore, no dispersion occurs in the dimension
of the bottom thickness T of the cup section 94 of the outer cup
obtained as the forged product 92. The dimensional accuracy of the
bottom thickness T of the cup section 94 is maintained highly
accurately.
The punch 40 is lowered as described above, and it arrives at the
forging end position shown in FIG. 2 from the forging start
position shown in FIG. 1. Thus, the forging is applied to the
forging material by the aid of the punch 40, the lower die 28, and
the upper die 26. The forging material causes plastic flow along
with the shape of the cavity 46.
After completion of the forging process, the punch 40 is raised to
the initial position integrally with the elevator unit 54 connected
to the ram in accordance with the driving action of the mechanical
press. Accordingly, the punch 40, the holder 80, and the guide
sleeve 82 are separated from the hole 32 of the first ring member
34, giving a waiting state for the next step. The forged product 92
(see FIG. 10) is taken out in accordance with the displacement
action of the knockout pin 48.
Next, explanation will be made with reference to a flow chart shown
in FIG. 11 for the function and effect of the hydraulic pressure
control apparatus 10 including, for example, the air vent circuit
127 and the relief pressure vent circuit 135.
It is assumed that the pressure oil having a predetermined
hydraulic pressure is previously charged in the pressure chamber 58
via the supply passage 118 and the passage 64 in accordance with
the driving action of the first hydraulic pump 132 (step S1).
The air vent valve 131 of the air vent circuit 127 is deenergized
to previously give the valve-open state. Therefore, the air, which
contaminates the pressure oil charged in the pressure chamber 58,
is discharged to the tank 110 via the passage 129 and the discharge
passage 108 together with a small amount of pressure oil leaked
from the pressure chamber 58. As a result, the air in the pressure
oil charged in the pressure chamber 58 is reliably removed.
After completion of the preparatory operation as described above,
the unillustrated controller energizes the solenoid-operated valve
so that the air vent valve 131 is in the valve-closed state (step
S2).
In the valve-closed state of the air vent valve 131, the pressure
sensor 121 detects the charge pressure of the pressure oil charged
in the pressure chamber 58 (see FIG. 12), and an obtained detection
signal is sent to the unillustrated controller. The controller
judges whether or not the charge pressure of the pressure oil in
the pressure chamber 58 is not less than the preset pressure on the
basis of the detection signal (step S3). If the charge pressure is
less than the preset pressure, a driving stop signal is sent to the
unillustrated mechanical press. As a result, the operation of the
mechanical press is immediately stopped. Accordingly, the punch 40
is held in the state of being stopped at the top dead center (step
S4). If the charge pressure of the pressure oil in the pressure
chamber 58 is not less than the preset pressure, the routine
proceeds to the next step S5.
In the step S5, the punch 40 is lowered in accordance with the
driving action to the mechanical press, and the forming process is
started for the forging material. Accordingly, the hydraulic
pressure of the pressure oil in the pressure chamber 58 is
increased. In this embodiment, the pressure sensor 121 detects the
hydraulic pressure of the pressure oil in the pressure chamber 58
at the initial stage of the forming process (see FIG. 12). An
obtained detection signal is sent to the unillustrated controller.
The controller judges from the detection signal whether or not the
hydraulic pressure of the pressure oil in the pressure chamber 58
at the initial stage of the forming to process is increased up to
the initial preset pressure (step S6). If the hydraulic pressure of
the pressure oil in the pressure chamber 58 is not increased to the
initial preset pressure, then it is judged that the forging
material is not charged in the cavity 46, and an energizing signal
is sent to the relief pressure vent valve 133 so that the relief
pressure vent valve 133 is in the ON state. Accordingly, the relief
control pressure for the relief valve 104 is subjected to the open
state (step S7).
That is, the valve position of the relief pressure vent valve 133
is switched. The pressure oil, which is stored in the relief
chamber of the relief valve 104, passes through the passage 137,
the relief pressure vent valve 133, and the passage 139, and it is
discharged to the tank 110 via the discharge passage 108.
Therefore, the relief control pressure is quickly reduced to be
zero, and the relief valve 104 is in the valve-open state. When the
valve position of the relief pressure vent valve 133 is switched,
the pilot pressure is supplied to the check valve 122. The check
valve 122 is in the valve-closed state, and the internal pressure
of the high pressure accumulator is maintained at the predetermined
pressure.
When the relief valve 104 is in the valve-open state, the inlet
port 106 communicates with the outlet port 112. The large volume of
the pressure oil charged in the pressure chamber 58 is sucked into
the low pressure accumulator 128 in accordance with the driving
action of the low pressure accumulator 128. As a result, the flow
passage resistance is reduced when the pressure oil having the
large volume charged in the pressure chamber 58 is discharged along
the discharge passage 108. Thus, it is possible to avoid the
occurrence of the surge pressure (see FIG. 9).
In this case, there is given the state in which no forging material
is charged. The pressure oil support load of the piston 60 acts on
the abutment portion between the first plate 44 and the second
plate 42. However, the relief valve 104 is in the valve-open state,
and the relief pressure of the relief valve 104 becomes zero.
Accordingly, the pressure oil support load, which is applied to the
abutment portion between the first plate 44 and the second plate
42, is zero. Thus, neither shock nor damage is applied to the upper
die and the lower die at all. In this process, the unillustrated
controller judges that the charge of the forging material is
abnormal. The punch 40 is raised in accordance with the driving
action of the mechanical press, and it is stopped upon arrival at
the top dead center (step S8).
Subsequently, if the hydraulic pressure of the pressure oil in the
pressure chamber 58 is increased to the initial preset hydraulic
pressure at the initial stage, the load sensor 45 is used to detect
whether or not the predetermined forming load is applied to the
forging material by the punch 40 (step S9).
That is, the load sensor 45 is used to detect the fact that the
first plate 44 and the second plate 42 make certain abutment. The
load sensor 45 sends a detection signal to the unillustrated
controller. The controller judges on the basis of the detection
signal whether or not the first plate 44 and the second plate 42
make abutment at not less than the predetermined load, and the
forging material is forged to have the predetermined thickness
dimension.
For example, as shown by a solid line in FIG. 13, when the output
of the load sensor 45 changes along a hill-shaped curve
corresponding to the change in hydraulic pressure of the pressure
oil in the pressure chamber 58, the controller judges that the
first plate 44 and the second plate 42 make abutment at not less
than the predetermined load, and the thickness dimension of the
forging material is regulated to be the predetermined thickness
dimension in accordance with the abutment of the dies.
On the contrary, when the forming load on the forging material is
higher than the pressure oil support load, and output of the load
sensor 45 corresponding to the change in hydraulic pressure of the
pressure oil in the pressure chamber 58 is linearly flat as shown
by a broken line in FIG. 13, then the controller judges that the
pressure oil is relieved without making the abutment between the
first plate 44 and the second plate 42, and the thickness dimension
of the forging material is not regulated by the abutment of the
dies.
The thickness dimension for the forging material can be made more
accurate such that the unillustrated controller feedback-controls
the relief pressure on the basis of the detection signal outputted
from the load sensor 45. That is, the controller sends, to the
pressure control valve 136, the relief pressure control signal
corresponding to the detection signal outputted from the load
sensor 45 to control the relief pressure corresponding to the
abutment load. Thus, the thickness of the forging material can be
regulated highly accurately.
If the abutment of the dies is not detected from the detection
signal outputted from the load sensor 45, then the controller
judges that the abutment of the dies is abnormal, and it outputs
the driving stop signal to the unillustrated mechanical press.
Accordingly, the punch 40 is raised, and then it is stopped at the
top dead center (step S10). If the predetermined forming load is
applied, the routine proceeds to the next step S11.
Subsequently, the forming load is applied to the forging material
by the punch 40. Before the punch 40 arrives at the bottom dead
center, the pressure sensor 121 detects the relief preset pressure
in the pressure chamber 58 (see FIG. 12), and a detection signal is
sent to the unillustrated controller. The unillustrated controller
judges whether or not the relief preset pressure is within the
predetermined range on the basis of the detection signal (step
S11).
If the relief preset pressure is not within the predetermined
range, the driving stop signal is outputted to the unillustrated
mechanical press. Accordingly, the punch 40 is raised, and then it
is stopped at the top dead center (step S12). If it is judged that
the relief preset pressure is within the predetermined range, the
routine proceeds to the next step S13.
In the next step S13, the pressure oil in the pressure chamber 58
is relieved in accordance with the displacement action of the
piston 60. The punch 40 arrives at the bottom dead center, and then
it is raised toward the top dead center. The following operation is
performed during the period in which the punch 40 arrives at the
bottom dead center, it is then raised, and it arrives at the top
dead center. That is, the pressure oil is charged again in the
pressure chamber 58 via the supply passage 118. The piston 60 is
restored to the initial position. Further, the unillustrated
controller is used to deenergize the solenoid-operated valve so
that the air vent valve 131 is in the valve-open state (steps S14
to S17).
When the steps as described above are continuously performed, the
forging process can be continuously applied to the forging
material.
In the first embodiment, it is detected that the forging material
is not charged in the cavity 46 at the stage of the initial
increase of the hydraulic pressure. The valve position of the
relief pressure vent valve 133 is switched so that the pressure oil
support load is made zero. Accordingly, the dies are prevented from
application of overload upon the abutment between the first plate
44 and the second plate 42. As a result, according to this
embodiment, the occurrence of stress in the die is avoided, the die
is prevented from breakage, and it is possible to improve the
durability of the die.
In the first embodiment, the variation amount, which is caused by
the elongation of, for example, the frame of the unillustrated
mechanical press and the connecting rod and which would otherwise
cause the fluctuation of the thickness dimension of the forging
material in ordinary cases, is absorbed as the change in stroke
amount of the piston 60. Further, the thickness dimension of the
material is determined by the abutment of the upper die and the
lower die. Therefore, no influence is exerted by the elongation of
the frame or the like.
In the first embodiment, the outer cup for constructing the
constant velocity universal joint is used as the forging material.
However, there is no limitation thereto. It is a matter of course
that the present invention is applicable to a variety of forged
products which require the dimensional accuracy in the thickness
direction of the part including, for example, stepped parts and
stepped gears which are not shown in the drawings.
Additionally, in the first embodiment, the buffering mechanism 56
is provided on the elevator unit 54 disposed on the displacement
side. However, there is no limitation thereto. The buffering
mechanism 56 may be provided on the fixed side, for example, on the
upper die 26 and the lower die 28.
Next, a forging die 210 according to a second embodiment of the
present invention is shown in FIG. 14. In the following
embodiments, the same constitutive components are designated by the
same reference numerals, detailed explanation of which will be
omitted.
The forging die 210 comprises a first die holder 214 which is
provided with a plurality of guide means 212a to 212d (see FIG. 17)
standing thereon in the vicinity of four corners, and a second die
holder 216 and a third die holder 218 which are provided in a
stacked manner at a central portion of the first die holder 214. A
thick-walled forcible insertion ring (cylindrical member) 220 is
fixed on the second die holder 216 by the aid of a clamping means
222.
As shown in FIG. 16, a first insert member 213, a second insert
member 215, and a third insert member 217, which are formed as ring
members in a divided manner, are joined in an integrated manner
along the axial direction in the hole of the forcible insertion
ring 220. In this embodiment, the outer diameter of each of the
first to third insert members 213, 215, 217 is designed to be
slightly larger than the inner diameter of the hole of the forcible
insertion ring 220. The first to third insert members 213, 215, 217
are fitted into the hole of the forcible insertion ring 220 by
means of shrinkage fitting as described later on. The first to
third insert members 213, 215, 217 function as a plurality of
annular members.
The first insert member 213 and the third insert member 217 are
made of, for example, a metal material of SKD 61 (based on JIS)
having a Rockwell hardness HRC of about 50. The second insert
member 215 is made of, for example, a cemented carbide material
having a Rockwell hardness HRA of about 88. Therefore, the second
insert member 215 is designed to have a larger hardness as compared
with the first insert member 213 and the third insert member
217.
As shown in FIG. 16, an annular projection 219 is formed at a lower
portion of the inner circumferential surface of the forcible
insertion ring 220. The annular projection 219 is fitted to an
annular recess 221 which is formed on the third insert member 217.
Thus, the downward displacement of the third insert member 217 is
regulated, and it is positioned in the hole of the forcible
insertion ring 220.
As shown in FIGS. 14 and 16, the clamping means 222 includes a
fixing plate 227 for engaging with a step section of the forcible
insertion ring 220, and a plurality of bolts 229 for holding the
fixing plate 227 on the first die holder 214.
An upper die 226 and a lower die 228, which are formed in a divided
manner, are joined in an integrated manner along the axial
direction at the inside of the first to third insert members 213,
215, 217. A cavity 224 for charging a forging material therein is
formed at the inside of the upper die 226 and the lower die 228.
The upper die 226 and the lower die 228 function as a die
member.
In this embodiment, the stress is concentrated on an inner wall
surface 223 of the lower die 228 when the forging process is
performed, corresponding to a joint portion of a cup section 286
and a shaft section 288 of an outer cup as a forged product 284
(see FIG. 21). The lower die 228, which has the inner wall surface
223 as described above, is externally fitted by the annular second
insert member 215 which is composed of the harder material.
Therefore, the rigidity is enhanced in the circumferential
direction approximately perpendicular to the axis. An annular
recess 225, which is engaged with the third insert member 217, is
formed on the lower side of the outer circumferential surface of
the lower die 228.
As shown in FIG. 14, a first ring member (ring member) 234, which
is formed with a hole 232 for forcibly inserting a punch 230
thereinto, is integrally joined to the upper surfaces of the upper
die 226 and the first insert member 213. A second ring member 236
having a large diameter, which is externally fitted to the first
ring member 234, is integrally joined onto the upper surface of the
forcible insertion ring 220.
In this embodiment, the second ring member 236 is fastened to the
forcible insertion ring 220 so that the first ring member 234 is
externally fitted thereby. Accordingly, a tapered surface 238,
which is formed on the second ring member 236, slidably contacts
with an inverse tapered surface 240 which is formed on the first
ring member 234. Thus, the force acts to press the first ring
member 234 downwardly.
An annular guide groove (not shown), which is used to guide the
punch 230 when the punch 230 is forcibly inserted, is formed at an
upper portion of the hole 232 of the first ring member 234. The
punch 230, which is forcibly inserted into the hole 232 of the
first ring member 234, has its one end which is formed with a
desired convex-concave configuration corresponding to a
concave-convex configuration of the product to be forged.
A knockout pin 244 for extruding the forged product is arranged
movably back and forth along a hole 246 formed through the second
die holder 216 and the third die holder 218, under the cavity 224
which is formed by the upper die 226 and the lower die 228. The
secondary formed product 52 as shown in FIG. 8 is charged as the
forging material in the cavity 224.
An elevator unit 250, which is connected to a ram of an
unillustrated mechanical press and which is displaceable in the
vertical direction integrally with the ram in accordance with the
driving action of the mechanical press, is provided over the
forcible insertion ring 220 at a position separated by a
predetermined distance. The punch 230 is fixed to the elevator unit
250 by the aid of a jig 252. A cylindrical guide sleeve (sleeve
member) 254, which is formed of a metal material, is externally
fitted to a predetermined portion of the outer circumference of the
punch 230.
As shown in FIG. 20, graphite 256 is embedded in a plurality of
holes of the guide sleeve 254. Accordingly, it is possible to well
maintain the lubrication characteristic when the guide sleeve 254
is forcibly inserted into the hole 232 of the first ring member
234. In this embodiment, the diameter on the outer circumferential
side of the guide sleeve 254 externally fitted to the punch 230 is
designed to be slightly larger than the diameter on the inner
circumferential side of the hole 232 of the first ring member
234.
It is preferable that the guide sleeve 254 is made of, for example,
a metal material such as SKD 11, FC 25, or FC 30 based on JIS, and
the first ring member 234 is made of a material which is harder
than that for the guide sleeve 254.
The punch 230 is displaceable in the vertical direction integrally
with the elevator unit 250 in accordance with the guiding action of
the plurality of guide means 212a to 212d provided in the
upstanding manner on the first die holder 214.
As shown in FIG. 18, the guide means 212a (212b to 212d) comprises
a lengthy main post body 258 which is fixed to the first die holder
214, a cylindrical cover member 260 which is connected to the
elevator unit 250 and which is displaceable integrally with the
elevator unit 250, a guide ring 264 which is provided to surround
the outer circumference of the main post body 258 and which is
slidably displaceable along the axial direction of the main post
body 258 by making engagement with an annular step section 262 of
the cover member 260, and a spring member 266 for supporting the
guide ring 264.
The guide ring 264 includes a plurality of arrays of holes 268
which are formed substantially in parallel to the axial direction.
Substantially columnar rolling members 270 are arranged rollably in
the holes 268. As shown in FIG. 19, flat first rolling surfaces
272, which extend along the axial direction and which are formed in
a plurality of arrays substantially in parallel to one another, are
formed on the outer circumferential surface of the main post body
258. On the other hand, flat second rolling surfaces 274, which are
opposed to the first rolling surfaces 272, are formed on the inner
wall surface of the cover member 260.
In this arrangement, the rolling members 270 roll in a state of
making line-to-line contact with the first rolling surfaces 272 and
the second rolling surfaces 274 respectively. Accordingly, the
cover member 260 connected to the elevator unit 250 and the guide
ring 264 engaged with the cover member 260 are displaced in an
integrated manner in the axial direction of the main post body
258.
Alternatively, the rolling members 270 may not be formed in the
holes 268 of the guide ring 264. It is also preferable that the
guide ring 264 is formed to surround the outer circumferential
surface of the main post body 258, and the guide ring 264 is
allowed to perform relative sliding displacement while making
surface-to-surface contact with the main post body 258.
The forging die 210 according to the second embodiment of the
present invention is basically constructed as described above.
Next, its operation, function, and effect will be explained.
Explanation will be made below for an illustrative case in which an
outer cup for constructing a constant velocity universal joint is
forged to obtain a forged product.
At first, explanation will be made for the assembling step for the
lower die section for constructing the forging die 210.
The third insert member 217, the second insert member 215, and the
first insert member 213 are successively inserted along the axial
direction of the hole of the forcible insertion ring 220. In this
procedure, the annular projection 219 of the forcible insertion
ring 220 is fitted to the annular recess 221 of the third insert
member 217. Accordingly, the downward displacement of the third
insert member 217 is regulated, and the components are positioned
in the hole of the forcible insertion ring 220 (see FIG. 16).
The outer diameter of each of the first to third insert members
213, 215, 217 is designed to be slightly larger than the inner
diameter of the hole of the forcible insertion ring 220. Therefore,
the hole of the forcible insertion ring 220 is heated and expanded
by using an unillustrated heating means, and the first to third
insert members 213, 215, 217 are fitted into the hole of the
forcible insertion ring 220 by means of the shrinkage fitting.
Subsequently, the lower die 228 and the upper die 226 are
successively inserted along the axial direction of the holes of the
first to third insert members 213, 215, 217. In this procedure, the
inner circumference of the third insert member 217 is fitted to the
annular recess 225 which is formed on the outer circumferential
surface of the lower die 228. Accordingly, the downward
displacement of the lower die 228 is regulated, and the components
are installed in the state of being positioned (see FIG. 16). The
lower die 228 is forcibly inserted strongly into the holes of the
second and third insert members 215, 217.
Further, the first ring member 234 is installed, which is engaged
with the upper surfaces of the upper die 226 and the first insert
member 213. The second ring member 236 is externally fitted to the
first ring member 234. Accordingly, the tapered surface 238, which
is formed on the second ring member 236, slidably contacts with the
inverse tapered surface 240 which is formed on the first ring
member 234. Thus, the force acts to press the first ring member 234
in the downward direction. The pressing force increases the surface
pressure at the joining surface between the upper die 226 and the
lower die 228, and hence it is possible to avoid any occurrence of
burr.
In this procedure, the upper die 226, the lower die 228, the first
to third insert members 213, 215, 217, and the other components are
assembled in an integrated manner in the state in which the punch
230 externally fitted with the guide sleeve 254 is inserted into
the hole 232 of the first ring member 234. Thus, the punch 230 is
positioned with respect to the cavity 224 which is formed by the
upper die 226 and the lower die 228. The assembling step for the
lower die section is completed as described above.
Next, explanation will be made for the forging steps for the
forging material.
The primary forging process is applied to a columnar billet 84 as
shown in FIG. 5 by using an unillustrated die apparatus to thereby
obtain a primary forged product 86 having different diameters of
those divided respectively by an intermediate step section as shown
in FIG. 6. Subsequently, the preliminary forming process is applied
to the primary forged product 86 (see FIG. 7), and then the
secondary forging process is performed by using another
unillustrated die apparatus. Thus, the secondary formed product 52,
which is composed of a cup section 88 and a shaft section 90 as
shown in FIG. 8, is obtained.
The forging die 210 according to this embodiment is used for the
secondary formed product 52 as a forging material to which the
tertiary forging process is further applied.
At first, the following preparatory operation is performed. That
is, it is assumed that the punch 230 is previously positioned with
respect to the cavity 224 which is formed by the upper die 226 and
the lower die 228 in the assembling step as described above.
The secondary formed product 52 as the forging material is charged
in the cavity 224 in a state in which the punch 230 is arranged at
an unillustrated raised position. The punch 230 is lowered
integrally with the elevator unit 250 joined to the ram (not shown)
in accordance with the driving action of the unillustrated
mechanical press to give the state shown in FIG. 14. Thus, the
forging process is started.
When the punch 230 is lowered integrally with the elevator unit
250, any unbalanced load in the transverse direction is preferably
absorbed by the plurality of (for example, four of) guide means
212a to 212d which are provided between the elevator unit 250 and
the first die holder 214. Accordingly, the punch 230 is smoothly
inserted under the pressure into the center of the first ring
member 234.
When the forging process is started, the guide sleeve 254, which is
externally fitted to the part of the outer circumferential surface
of the punch 230, advances in accordance with the guiding action of
an annular guide groove (not shown) formed at the upper end of the
hole 232 of the first ring member 234, and the punch 230 is further
lowered. Accordingly, the punch 230 and the guide sleeve 254 are
displaced in an integrated manner in a state of being forcibly
inserted into the hole 232 of the first ring member 234.
Thus, the punch 230 is lowered, and it arrives at the forging end
position shown in FIG. 15 from the forging start position shown in
FIG. 14. Accordingly, the forging is applied to the forging
material by the aid of the punch 230, the lower die 228, and the
upper die 226. The forging material is subjected to plastic flow
along with the shape of the cavity 224.
After completion of the forging process as described above, the
punch 230 is raised to the predetermined position integrally with
the elevator unit 250 connected to the ram (not shown) in
accordance with the driving action of the unillustrated mechanical
press. Accordingly, the punch 230 and the guide sleeve 254 are
separated from the hole 232 of the first ring member 234, giving a
waiting state for the next step. The forged product 284 (see FIG.
21) is taken out in accordance with the displacement action of the
knockout pin 244.
In the second embodiment, the stress acts on the portion at which
the stress is concentrated on the die when the forging process is
performed, i.e., the inner wall surface 223 of the lower die 228
corresponding to the joint portion of the cup section 286 and the
shaft section 288 of the outer cup obtained as the forged product
284. However, the lower die 228 is externally fitted by the annular
second insert member 215 which is composed of the harder material,
and thus the rigidity is secured in the radial direction
substantially perpendicular to the axis. Accordingly, it is
possible to suppress the strain (deformation) of the die which
would be otherwise caused by the stress.
Therefore, even when the forging process is continuously performed
for a long period of time by using the forging die 210 according to
the second embodiment, then the service life is prolonged as
compared with the die concerning the conventional technique, and it
is possible to improve the durability. As a result, it is possible
to reduce the cost of the die.
When the pressurizing force is applied to the forging material, the
guide sleeve 254, which is externally fitted to the punch 230, is
in the state of being forcibly inserted into the hole 232 of the
first ring member 234. Accordingly, the punch 230 is lowered while
maintaining the forcible inserted state.
Therefore, in the second embodiment, the pressurizing force is
applied to the forging material in the state in which the punch 230
is forcibly inserted by the aid of the guide sleeve 254 into the
hole 232 of the first ring member 234. The punch 230 does not cause
any centering deviation in the transverse direction. Therefore, as
shown in FIG. 21, it is possible to highly accurately maintain the
coaxiality between the axis E of the cup section 286 and the axis F
of the shaft section 288 of the outer cup obtained as the forged
product 284. In this embodiment, the deflection of the shaft
section 288 of the outer cup was successfully suppressed to be, for
example, not more than 0.06 mm.
The guide sleeve 254 is made of the metal of the type which is
different from that for the first ring member 234. Further, the
graphite, which is embedded in the guide sleeve 254, is used to
well retain the lubrication characteristic. Thus, it is possible to
suppress the occurrence of scuffing on the sliding surfaces of the
guide sleeve 254 and the first ring member 234.
The guide sleeve 254 is provided detachably with respect to the
punch 230 by the aid of the jig 252. Accordingly, it is
advantageous that the guide sleeve 254 can be conveniently
exchanged with another new guide sleeve 254.
In addition, for example, the outer circumferential surface of the
cup section 286 of the outer cup, which is the attachment site of a
pulser (not shown), can be directly ground.
Next, a forging die 310 according to a third embodiment of the
present invention is shown in FIG. 22.
The forging die 310 includes a forcible insertion ring 320 which is
formed to have a substantially cylindrical configuration. A first
insert member (first annular member) 313 and a second insert member
(second annular member) 315, which are formed as ring members in a
divided manner respectively, are integrally joined in the axial
direction in the hole of the forcible insertion ring 320 (see FIG.
24). Each of the first and second insert members 313, 315 is made
of, for example, a metal material of SNCM 439 (based on JIS) having
a Rockwell hardness HRC of about 40.
As shown in FIGS. 25 and 26, clearances 317a, 317b, which are
available when the first and second insert members 313, 315 are
forcibly inserted with ease into the hole of the forcible insertion
ring 320, are formed on the upper side of the forcible insertion
ring 320 and the lower side of the second insert member 315
respectively.
As shown in FIG. 24, an annular projection 319 is formed at a lower
portion of the inner circumferential surface of the forcible
insertion ring 320. The annular projection 319 is fitted to an
annular recess 321 which is formed on the second insert member 315.
Thus, the downward displacement of the second insert member 315 is
regulated, and it is positioned in the hole of the forcible
insertion ring 320.
An upper die 326 and a lower die 328, which are formed in a divided
manner, are joined in an integrated manner along the axial
direction at the inside of the first and second insert members 313,
315. A cavity 224 for charging the forging material therein is
formed at the inside of the upper die 326 and the lower die 328.
The upper die 326 and the lower die 328 function as a die
member.
As shown in FIG. 22, a first ring member 334 formed with a hole 332
for forcibly inserting a punch 230 therein, and a second ring
member 335 provided integrally with the first ring member 334 are
joined to the upper surfaces of the upper die 326 and the first
insert member 313. A clamping ring 336 having a large diameter,
which is externally fitted to the second ring member 335, is
integrally joined to the upper surface of the first insert member
313. Alternatively, it is allowable to use an unillustrated ring
member in which the first ring member 334 and the second ring
member 335 are integrated into one unit.
In this embodiment, the clamping ring 336 is clamped into the hole
of the forcible insertion ring 320. Accordingly, the first ring
member 334 and the second ring member 335 are externally fitted by
the clamping ring 336. A tapered surface 338, which is formed on
the clamping ring 336, slidably contacts with an inverse tapered
surface 340 which is formed on the second ring member 335. Thus,
the force acts to press the first ring member 334 downwardly.
The forging die 310 according to the third embodiment of the
present invention is basically constructed as described above.
Next, its operation, function, and effect will be explained.
At first, explanation will be made for the assembling step for the
lower die section for constructing the forging die 310.
The second insert member 315 and the first insert member 313 are
successively inserted along the axial direction of the hole of the
forcible insertion ring 320. In this procedure, the annular
projection 319 of the forcible insertion ring 320 is fitted to the
annular recess 321 of the second insert member 315. Accordingly,
the downward displacement of the second insert member 315 is
regulated, and the components are positioned in the hole of the
forcible insertion ring 320.
The first and second insert members 313, 315 are forcibly inserted
smoothly with ease by the aid of the clearances 317a, 317b formed
on the forcible insertion ring 320 and the second insert member 315
respectively (see FIGS. 25 and 26).
Subsequently, the lower die 328 and the upper die 326 are
successively inserted along the axial direction of the holes of the
first and second insert members 313, 315. The upper die 326 and the
lower die 328 are forcibly inserted strongly into the holes of the
first and second insert members 313, 315.
Further, the first ring member 334 and the second ring member 335
are installed, which are engaged with the upper surfaces of the
upper die 326 and the first insert member 313. The clamping ring
336 is externally fitted to the second ring member 335.
Accordingly, the tapered surface 338, which is formed on the
clamping ring 336, slidably contacts with the inverse tapered
surface 340 which is formed on the second ring member 335. Thus,
the force acts to press the first ring member 334 in the downward
direction. The pressing force increases the surface pressure at the
joining surface between the upper die 326 and the lower die 328,
and hence it is possible to avoid any occurrence of burr.
In this procedure, the upper die 326, the lower die 328, the first
and second insert members 313, 315, and the other components are
assembled in an integrated manner in the state in which the punch
230 externally fitted with the guide sleeve 254 is inserted into
the hole 332 of the first ring member 334. Thus, the punch 230 is
positioned with respect to the cavity 224 which is formed by the
upper die 326 and the lower die 328. The assembling step for the
lower die section is completed as described above.
In the third embodiment, the first and second insert members 313,
315 are forcibly inserted with ease into the hole of the forcible
insertion ring 320. Further, the structure is formed to be simple.
Accordingly, the die, which has been once assembled, can be
disassembled easily and conveniently. Thus, it is possible to
improve the dividing performance. Therefore, the maintenance
operation can be easily performed, and the maintenance performance
is improved.
In the third embodiment, when the forging process is performed,
even if the stress is applied radially outwardly to the upper die
326 and the lower die 328, then the first and second insert members
313, 315, which are forcibly inserted with ease into the hole of
the forcible insertion ring 320, are displaced by a minute distance
radially outwardly. Thus, the stress can be preferably
absorbed.
Therefore, the strain of the die resulting from the stress is
suppressed, and thus it is possible to prolong the service life of
the die. Even when the die is worn due to the secular change as a
result of the use for a long term, it is enough that only the lower
die 328, on which the stress is concentrated, is exchanged with a
new lower die 328. Therefore, it is possible to reduce the cost of
the die.
Further, the third embodiment adopts the simple structure in which
the upper die 326 and the lower die 328 are externally fitted by
the first and second insert members 313, 315. Thus, it is possible
to further reduce the cost of the die.
The other construction, function, and effect are the same as those
of the second embodiment described above, detailed explanation of
which is omitted.
Next, a forging die 410 according to a fourth embodiment of the
present invention is shown in FIG. 27.
The forging die 410 includes a forcible insertion ring 420 which is
formed to have a substantially cylindrical configuration. A
cylindrical sleeve member (annular member) 426 is forcibly inserted
into a hole 424 of the forcible insertion ring 420. An upper die
430 and a lower die 432, which are formed as ring members in a
divided manner respectively, are forcibly inserted into the hole
428 of the sleeve member 426 in a state of being integrally joined
in the axial direction (see FIG. 28). The upper die 430 and the
lower die 432 function as a die member.
As shown in FIG. 28, a tapered surface 434, which has its inner
diameter gradually decreasing upwardly, is formed on the upper side
of the hole 428 of the sleeve member 426. The tapered surface 434
presses the upper die 430 downwardly. Thus, the tapered surface 434
functions to avoid any occurrence of burr by increasing the surface
pressure at the joined surface between the upper die 430 and the
lower die 432.
A cavity 440 for charging the forging material therein is formed at
the inside of the upper die 430 and the lower die 432. As shown in
FIG. 29, an inclined surface 446, which is inclined by a
predetermined angle .theta. with respect to the vertical plane, is
formed on the inner wall surface of the lower die 432 for forming
the cavity 440, i.e., at a portion corresponding to a step section
444 of a forged product 442 (see FIG. 33). A curved section 448,
which has a circular arc-shaped cross section with a large radius
of curvature, is continuously formed under the inclined surface
446. The inclined surface 446 and the curved section 448 function
as a stress-suppressing mechanism. In FIG. 29, the predetermined
angle .theta. of the inclined surface 446 is set to be about 15
degrees.
As shown in FIG. 27, a first ring member 455 formed with a hole 453
for forcibly inserting a punch 452 therein, and a second ring
member 457 formed integrally with the first ring member 455 are
joined to the upper surfaces of the upper die 430 and the sleeve
member 426. A clamping ring 459 having a large diameter, which is
externally fitted to the second ring member 457, is integrally
joined to the upper surface of the forcible insertion ring 420.
Alternatively, it is allowable to use an unillustrated ring member
in which the first ring member 455 and the second ring member 457
are integrated into one unit.
In this embodiment, the clamping ring 459 is clamped into the hole
of the forcible insertion ring 420. Accordingly, the first ring
member 455 and the second ring member 457 are externally fitted by
the clamping ring 459. A tapered surface, which is formed on the
clamping ring 459, slidably contacts with an inverse tapered
surface which is formed on the second ring member 457. Thus, the
force acts to press the first ring member 455 downwardly.
The forging die 410 according to the fourth embodiment of the
present invention is basically constructed as described above.
Next, its operation, function, and effect will be explained.
Explanation will be made below for an illustrative case in which an
outer cup for constructing a constant velocity universal joint is
forged to obtain a forged product.
At first, explanation will be made for the forging steps for the
forging material.
The primary forging process is applied to a columnar billet (not
shown) by using an unillustrated die apparatus to thereby obtain a
primary forged product 478 having different diameters of those
divided respectively by an intermediate step section as shown in
FIG. 30. Subsequently, the preliminary forming process is applied
to the primary forged product 478 (see FIG. 31), and then the
secondary forging process is performed by using another
unillustrated die apparatus. Thus, the secondary formed product
465, which is composed of a cup section 480 and a shaft section 482
as shown in FIG. 32, is obtained.
The forging die 410 according to the fourth embodiment is used for
the secondary formed product 465 as a forging material to which the
tertiary forging process is further applied. The following
preparatory operation is performed. That is, it is assumed that the
punch 452 is previously positioned with respect to the cavity 440
which is formed by the upper die 430 and the lower die 432.
The secondary formed product 465 as the forging material is charged
in the cavity 440 in a state in which the punch 452 is arranged at
an unillustrated raised position. The punch 452 is lowered
integrally with the elevator unit 250 joined to the ram (not shown)
in accordance with the driving action of the unillustrated
mechanical press to give the state shown in FIG. 27. Thus, the
forging process is started.
When the forging process is started, the guide sleeve 254, which is
externally fitted to the part of the outer circumferential surface
of the punch 452, advances in accordance with the guiding action of
an annular guide groove (not shown) formed at the upper end of the
hole 453 of the first ring member 455, and the punch 452 is further
lowered. Accordingly, the punch 452 and the guide sleeve 254 are
displaced in an integrated manner in a state of being forcibly
inserted into the hole 453 of the first ring member 455.
Thus, the punch 452 is lowered, and it arrives at the forging end
position from the forging start position shown in FIG. 27.
Accordingly, the forging is applied to the forging material by the
aid of the punch 452, the lower die 432, and the upper die 430. The
forging material is subjected to plastic flow along with the shape
of the cavity 440.
After completion of the forging process as described above, the
punch 452 is raised to the predetermined position integrally with
the elevator unit 250 connected to the ram (not shown) in
accordance with the driving action of the unillustrated mechanical
press. Accordingly, the punch 452 and the guide sleeve 254 are
separated from the hole 453 of the first ring member 455, giving a
waiting state for the next step. The forged product 442 (see FIG.
33) is taken out in accordance with the displacement action of the
knockout pin 244.
Explanation will now be made for the stress which is generated when
the forged product 442 is taken out of the upper die 430 and the
lower die 432 by the aid of the knockout pin 244.
FIG. 34 shows a magnified longitudinal sectional view illustrating
a state in which the step section 444 of the forged product 442 is
separated from the inner wall surface of the lower die 432
according to the fourth embodiment by being pressed upwardly by the
knockout pin 244. FIG. 35 shows a magnified longitudinal sectional
view illustrating a state in which the step section 488 of the
forged product 486 is separated from an inner wall surface of a
lower die 484 concerning Comparative Example.
In Comparative Example shown in FIG. 35, the inner wall surface 490
of the lower die 484, which corresponds to the step section 488 of
the forged product 486, is formed along the vertical plane. When
the forged product 486 is pressed upwardly (in the direction
indicated by the arrow) by the knockout pin 244, the following
inconvenience arises. That is, the stress is concentrated on the
predetermined position 492 of the inner wall surface 490 of the
lower die 484 corresponding to the step section 488, resulting in
occurrence of any crack.
On the contrary, in the fourth embodiment shown in FIG. 34, the
inclined surface 446, which is inclined by the predetermined angle
with respect to the vertical plane, is formed at the portion
corresponding to the step section 444 of the forged product 442.
Further, the curved section 448 is formed, which has the circular
arc-shaped configuration and which continues to the inclined
surface 446.
Therefore, in the fourth embodiment, when the forged product 442 is
pressed upwardly by the knockout pin 244, then the plastic strain,
which is generated between the outer circumferential surface of the
step section 444 of the forged product 442 and the inner wall
surface of the lower die 432, is dispersed, and thus the stress
concentration is mitigated. In other words, the contact surface
pressure, which is generated between the outer circumferential
surface of the step section 444 of the forged product 442 and the
inner wall surface of the lower die 432, is deflected from the
predetermined position 492. Thus, the stress, which is applied to
the inner wall surface of the lower die 432, can be dispersed, and
the stress can be suppressed. As a result, the inner wall surface
of the lower die 432 is prevented from occurrence of any crack.
Therefore, the durability of the die can be improved, and the cost
of the die can be reduced.
Further, the fourth embodiment is constructed as follows. That is,
when the pressurizing force is applied to the forging material, the
guide sleeve 254, which is externally fitted to the punch 452, is
in the state of being forcibly inserted into the hole 453 of the
first ring member 455. The punch 452 is lowered while maintaining
the forcibly inserted state described above.
Therefore, the pressurizing force is applied to the forging
material in the state in which the punch 452 is forcibly inserted
into the hole 453 of the first ring member 455 by the aid of the
guide sleeve 254. The punch 452 does not cause any positional
deviation in the transverse direction. Accordingly, as shown in
FIG. 33, it is possible to highly accurately maintain the
coaxiality between the axis E of the cup section 494 and the axis F
of the shaft section 496 of the outer cup obtained as the forged
product 442. In this embodiment, the deflection of the shaft
section 496 of the outer cup was successfully suppressed to be, for
example, not more than 0.06 mm.
* * * * *